Telephone apparatus



April 30, 1929. A. F. BENNETT 1,711,258

TELEPHONE APPARATUS Filed Aug. 2O 1925 I Patented Apr. 30, 1929.

UNITED STATES 1,111,258 PATENT oFFIcE.

ARTHUR F.-BENNETT, F RlCI-IIIIVIONDl HILL NEW YORK, lSSIG'NOR T0 WESTERNELECTRIC COMPANY, INCOREORATED, OF NEW YORK, N. Y., A. CORPORATION 0FNEW YORK.

TELEPHONE APPARATUS.

Application led August 20, 1925. 4Serial No. 51,301.

This invention relates to acoustic devices and particularly to'telephonetransmitters. An object of the invention is to\ improve the operation oftelephone transmitters and to etlect economies in their manufacture. Inaccordance with one feature of "the invention a telephone transmitter isprovided With a light, substantially aperiodic diaphragm having itscentral portion, which 1o forms a closure for the chamber containingthegranular carbon, slightly dished to control resistance changes due tothe thermal action ot' the carbon button.

Another feature provides for rictionally securing the elements ofso-called book damping meanstogether to make handling ot' the separateelements unnecessary.

In the specific embodiment hereinafter described as applied to atransmitter, the diaphragm is conical in shape with a center portionpractically iat but sufficiently conical or dished to compensate for thethermal action of the carbon button, with respect to which it forms aclosure and acts as'an agitator for the carbon material. The peripheryis provided with a channel and the conical surace of the diaphragm isprovided with radial corrugations. The diaphragm is mounted between bookdamping members 3o disposed on each side at its periphery to control itsvibrations and permit free radial expansion and contraction. Between thecarbon and the central portion of the diai phragm is disposed anotherbook damping element which serves to some extent to control the action othe diaphragm and at the same time to prevent the leakage ot' the carbongranules from the chamber.

The book damping members consist 'of rings ot paper or foil stacked and,in accordance with the invention, these rings are pierced with asuitable tool, such as a needle, to form telescoping projectionsor/burrs, the burrs on adjacent sheets frictionally engaging to securerictional hold.

Referring to the drawings Fig. 1 is a cross sectional view of amicrophone transmitter embodying the invention;

Fig. 2 is a front view ot the diaphragm; Fig. 3 is a plan view of one ofthe mounting and damping members, and

Fi g. 4 is a cross vsectional View through the mounting and dampingmembers on line 4-4 of Fig. 3.

' member 5.

A cup-shaped member 5 is provided with a central aperture formed by aninternally extended cylindrical portion 6, and an oli-set threaded rimhaving a ledge 7. The inner edge of the portion 6 is provided with aninwardly projecting flange 8 and an annular recess 9. The flange 8 formsone electrode of a barrier type transmitter button such as is disclosedin U. S. Patent 1,565,581 granted to C. R. Moore on Dec. 15, 1925. Anannular member 10 forms the other electrode of the carbon button and isinsulated from the cylindrical portion 6 by insulating members 11, 12,and 13. The chamber formed by the electrodes 8 and 10 is closed at'oneend y a disc 15 provided with a terminal 16. The inner surface of thedise' 15 is preferably covered with a suitable insulating material 17 toinsulate it from the carbon granules. The electrode 10 and itsinsulating members are secured in place by a nut 19 having threadedengagement with the cup rl`he other side of the carbon chamber is closedby a diaphragm 20 and a plurality ot' thin annular members 21 made ot'paper or foil and loosely disposed in the recess 9 between the diaphragm2O and the electrode 8. These rings, in addition to preventing thegranular carbon from escaping, provide damping for controlling thevibra- S5 tions of the diaphragm. Since they are not packed tightly, airilms are permitted to form between adjacent rings which serve todissipate the energy according to well known theories of air damping.The dia- 90 phragm 2O is loosely supported on the ledge 7 between stacksof thin rings 22 and 23 by means of washer 24 and nut 25 which has,threaded engagement with the case 5. These rings act as air dampingmeans as described and claimed in U'. S. Patent 1, 660,990, granted toH. F. Dodge on Feb. 28, 1928. Between the book damping member 22 and thewasher 24 is a moisture-proof diaphragm 40:

The unit described herein may be sup- 10o ported in the usualtransmitter casing comprising a face plate 26 and a bell 27.'Preferably,d the unit is insulated from the face plate by an insulatingwasher 28 and secured thereto by means of an annular member 29 105 ofinsulating material and screws 30. Between the face plate 26 and the nut28 is a Wire gauze protecting member 41.

The diaphragm 20 is conical in form and made of aluminum alloy,magnesium 11o or any light material. Duralumin havinga thickness of .002to .003 has been found very satisfactory for kthe. purposes of theinvention. It is stiilened by radial corrugations to prevent the surfacefrom vibrat` ing smaller areas and a channel 31 is formed in theperiphery for stifening it. The channel 31 is preferably maderectangular in cross section in order to provide suitable seatingsurface for the book damping members 22 and 23 and its outer edge ispreferabl lower than its inner edge.

llhe central portion 32 of the diaphragm is slightly conical in form butonly sufficient to compensate by thermal expansion for changes in volumeof the electrode chamber, as described in U. S. Patent 1,570,120,granted to me on Jan. 19, 1926. It is also provided with radialcorrugations to give it stiffness. As shown -in the drawing, the

transmitter button is mounted on the convex side of the diaphragm.Obviously, however, it may be mounted on the concave side of thediaphragm in any well known manner in Which case the central portionshould Abe dished in the opposite direction to the outer portion.

For convenience in handling the damping rings of each of the bookdamping elements 21, 22 and 23/'are punched or stamped from the requirednumber of sheets of material and at the same time are pierced with asharp pointed tool such as a needle. The burrs of adjacent elementsinterlock vas shown in Fig. 4 to hold them together and make itunnecessary to handle the individual rings. It is preferable in piercingthe damping rings to pierce them near one edge so as to leave theremaining portion of the rings loose enough for air films to formbetween them. To accommodate the burrs, it is necessary to provide adepression either in the mounting or in the diaphragm. In the presentcase, the channel 31 in the periphery of the diaphragm providesdepressions on each side thereofI for the burrs in the damping rings 22and 23` The central portion 32 being slightly depressed, provides aslight shoulder permitting the burrs on the damping means 21 to beturned toward the diaphragm. The burrs on the damping means 21, 22 and23 engage the diaphragm and prevent the damping means from shft- What isclaimed is: v

1. An acoustic device 4comprising a diaphragm having a U shapedperipheral flange, damping means disposed against said flange forcontrolling the action of the diaphragm, said damping means comprising aplurality of thin washers having interlocking burrs, the burrsprojecting into the recess provided by said flange.

2. In a telephone transmitter, a carbon containing chamber, a diaphragm,the central portion of. which is in operative relation the carbon insaid chamber, damping means between the Walls of said chamber and saiddiaphragm, and additional dam ing means disposed 011 each side of theperip iery of said diaphragm and forming a. mounting therefor, saiddamping means comprising a bundle of rings of thin sheet materialsecured together by a plurality of interlocking burrs oneach adjacentring.

3. In an acoustic device, a diaphragm comprising a centrally disposedconicalshape portion having radial corrugations and a radiallycorrugated conical outer portion of different slope, said outer' portionhaving at its periphery a cylindrical flange, said fiange forming onewall of a rectangular corrugation in said diaphragm and means supportingsaid diaphragm for substantially free movement.

4. In a telephone transmitter, the combination of a carbon chamber, alight, stiff diaphragm in the form of a truncated cone having a radiallycorrugated cent1-al portion forming a closure for said carbon chamber,said central portion being slightly dished or set in the direction ofthe carbon chamber, a main portion having a radially corrugated conicalsurface, a peripheral portion having a concentric corrugation ofrectangular cross-section and book-damping means on each side of saidperipheral portion and between the edge 0f said carbon chamber and thediaphragm.

In witness whereof, I hereunto subscribe my name this 14th day ofAugust, A. D. 1925.

ARTHUR F. BENNETT.

